Heat exchangers of the type which are employed in automobiles, for example, as charged air coolers for turbochargers, comprise a manifold in the form of separate tank and header parts which are joined together to define a manifold housing. This housing is connected to a large number of heat exchange tubes through which air to be cooled is passed. The heat exchange tubes are connected at end portions thereof to the header part.
Such manifolds are subject to expansions arising from elevated temperatures and pressures, which render them liable to failure. Conventionally, the tank parts are reinforced to resist this expansion by the provision of increased wall thickness, the addition of internal and/or external ribbing, or the addition of internal tie bars which extend between inner walls of the tank, and which are cast with the tank or are welded in position. An increase in the header material gauge may also be employed as a means of reinforcement.
There are a number of problems with these means of strengthening. The addition of extra material for strengthening adds weight and increases the cost of the tank. It also complicates the tooling, patterns, moulds etc which are required. Where internal tie bars are welded into position within the tank there is a risk of catastrophic failure should a weld joint fail or a tie bar become dislodged. Where the tie bars are cast in position, this complicates the manufacture, and may require secondary operations to complete the casting, or the use of more than one sand core. Such casting procedures also require additional cleansing in order to remove residue created during this additional casting.
It has previously been proposed in French Patent Appliation, published No. 2614980 to provide in a plastics tank a transverse generally U-shaped strengthening wire which is fitted across the tank housing, legs of which are received in bores moulded into opposite sides of the tank. It is, however, particularly difficult to locate the wires in the bores since the ends of the wires must be aligned exactly with the bores before they can be received therein. Also, although these provide a strengthening function in a plastics tank, such wires would be quite inadequate for strengthening a cast metal tank for use as a charged air cooler tank.